The present disclosure relates to the field of display technology, and particularly, to a pixel circuit and a driving method thereof, a display panel, and a display device.
Currently a typical quantum dot light emitting diode (QLED) structure includes an electron transport layer, a hole transport layer, and a quantum dot light emitting layer. The hole transport layer and the electron transport layer may include organic small molecules, organic polymer, or inorganic metal oxides. The arrangement of the hole transport layer and the electron transport layer enables the light emitting efficiency of the quantum dot light emitting diode to rise from the initial less than 0.1% to about 10%, but the mismatch of the highest occupied molecular orbital (HOMO) energy levels between the hole transport layer and the quantum dot light emitting layer cause the quantum dots charge injection efficiency to remain low. Further, the quantum dots charge injection is unbalanced and the quantum dots represent non-electric-neutral. Compared with conventional organic electroluminescent light emitting diodes (OLEDs), the drawback of charge injection imbalance of quantum dot electroluminescent light emitting diodes (QLEDs) limits their light emitting lifetime and efficiency.
In the prior art, the problem is mainly improved in the following three ways. The first way is to increase the HOMO energy level of the hole transport layer to match the HOMO energy level of the quantum dot light emitting material as closely as possible. The second way is to increase the mobility rate and injection efficiency of holes by providing a hole enhancing layer. The third way is to slow down the injection rate of electrons by providing an electronic barrier layer, improving the recombination efficiency of electrons and holes. With regards to the first way, it is difficult to synthesize or find a material necessary for constituting the hole transport layer. With regards to the second way, it is necessary to provide a multilayer hole transport layer, which increases the difficulty of the process. With regards to the third way, excited photons cannot be increased. Thus, it is difficult to improve the light emitting efficiency.